Trocarless rotational entry cannula

ABSTRACT

A cannula for safely and easily gaining access to a body cavity without the use of a trocar, has screw threads on its outer surface and a lumen within the cannula extending throughout the entire length of the cannula. The distal end of the cannula is shaped, along its periphery, to penetrate and/or cut tissue layers of the body wall to gain access to a body cavity. The lumen is sufficiently large throughout its length to allow passage of instruments from the proximal end of the cannula directly into the body cavity, once the cannula has been inserted. A method for gaining access to a body cavity with the cannula is also described.

This invention relates to devices for gaining access to various bodycavities for endoscopic procedures, and more particularly to astabilized trocarless cannula for gaining access to the peritonealcavity for laparoscopic procedures with or without videoscopy bypenetrating a patient's anterior abdominal wall.

BACKGROUND OF THE INVENTION

The surgical procedures of endoscopy, including laparoscopy, with orwithout videoscopy, are in common use at the present time. The primaryadvantage of a laparoscopy is that only a small incision is required toaccess an area where a wide range of surgical procedures can beperformed through the small incision with minimal morbidity. Until thepresent invention, access to the peritoneal cavity during laparoscopyhas been gained by the use of a trocar assembly, i.e. a surgicalinstrument comprising two major components, a trocar (obturator) and acannula (trocar tube), as described below. The distal end of the cannulaof the trocar assembly is blunt and therefore relies on the ability ofthe trocar to pierce the various layers of the anterior abdominal wallto gain access to the peritoneal cavity. Traditionally, in preparationfor a laparoscopy, a small incision corresponding in size to about thediameter of the cannula, is made in the skin and underlying tissues downto and sometimes including an even smaller incision in the anteriorfascial sheath sufficient in size to accommodate the tip of the trocar.A Veress needle is then inserted through the incision and underlyingtissues into the peritoneal cavity, the peritoneal cavity is insufflatedwith CO₂ gas, and the Veress needle is withdrawn from the peritonealcavity prior to insertion of the trocar assembly. The distal end of thetrocar disposed within the cannula is then placed so that it is incontact with the layers of the body wall exposed by the incision and thetrocar is inserted through the tissues. By applying pressure against theproximal end of the trocar, the sharp pointed distal end of the trocaris forced through the different layers of the abdominal wall until itenters the peritoneal cavity carrying the cannula with it. The trocar isthen withdrawn, leaving the cannula as an access-way to the peritonealcavity. Various types of surgical and video instruments are insertedthrough the cannula into the peritoneal cavity permitting many kinds ofsurgical procedures to be performed within a patient's abdomen.

There are a number of disadvantages associated with the use ofconventional laparoscopic trocars. The principal disadvantages arefirstly that significant initial force is usually required to insert thetrocar through the layers of the anterior abdominal wall and secondly,that it is a "blind" procedure. The initially applied force may resultin the trocar being inadvertently inserted further into the abdominalcavity than is necessary or desirable, and it is not at all unusual insuch a situation for the trocar to result in an injury to a major bloodvessel or to other visceral organs in the patient's abdomen. Theseinjuries may be of a serious nature, and may even be fatal.

As used below, the term trocar refers to a solid sharp pointedinstrument or obturator which is inserted through a trocar tube orcannula, a cannula being a hollow sheath or sleeve, which is capable ofreceiving surgical instruments, equipment for endoscopic visualizationand videoscopy and gas or liquid. The term "distal end" applied to aninstrument refers to the end of the instrument that is introduced intothe body, and the term "proximal end" refers to the end that remainsoutside the body during the procedure.

The development and widespread use of trocars for endoscopy has servedto focus on the shortcomings and problems to be solved in the design ofdevices used for accessing body cavities, including the abdominalcavity. Although there have been many modifications and improvements intheir design, the problems discussed above have not been overcome. Anexample of such a modification is a trocar having a retractable sleeve.As soon as the sharp tip of the trocar enters the peritoneal cavity, aspring mechanism should cause the sleeve to snap over the sharp tip ofthe trocar and in this way prevent injury to any organs that the trocartip contacts. However, this mechanism may fail. As a result of the forceapplied to the trocar, the trocar tip pushes the peritoneum ahead of it,and causes forward "tenting" of the peritoneum before and while the tippenetrates the peritoneum. As penetration occurs, the peritoneumsurrounding the trocar tip so closely embraces the trocar tip that thepassage of the sleeve through the hole in the peritoneum is prevented ordelayed. If the sleeve fails to cover the entire tip of the trocar as itpenetrates the peritoneum, injuries to intra-abdominal organs by thetrocar tip or its sharp beveled edges will not be prevented.

Although trocar assemblies have been modified in various ways, no devicehas been disclosed using only a cannula, i.e. without a trocar, to gainaccess to the abdominal cavity. U.S. Pat. No. 5,147,376 discloses atrocar needle having a threaded truncated cone bit having a cuttingblade with a rounded edge at its truncated cone end. U.S. Pat. No.4,191,191 describes an elongated sharp pointed instrument for insertionthrough an elongated cannula, the sharp pointed instrument having screwthreads at its tip, and the proximal portion of the instrument includinga crank assembly. U.S. Pat. No. 5,217,441 describes a trocar penetrationdepth indicator having two threaded sleeves through which a trocar isinserted. U.S. Pat. No. 5,258,003 discloses a trocar which is insertedthrough a cannula, the trocar having a tapered distal end with screwthreads formed on the outer surface of the distal end. The distal endterminates in a flexible tip, through which a hollow needle passes. Theneedle communicates with a means for indicating changes in pressure asthe distal end of the needle enters the peritoneal cavity. U.S. Pat. No.5,209,736 describes a trocar assembly device including an outer, largerdiameter trocar tube and an inner, smaller diameter trocar tube, whichextends distally beyond a distal end portion of the outer trocar tube.The distal end of the inner smaller trocar tube is tapered, the taperedend bearing threads on its outer surface to facilitate insertion of thetrocar through the layers of the body.

In the above-mentioned patents and in currently used instruments, thetrocar or the instrument within the cannula pierces or cuts the bodylayers and gains access to the peritoneal cavity. Furthermore, theprogress of the trocar is achieved as a result of a force that isapplied to the proximal end of the trocar, the force being appliedsubstantially perpendicular to the skin surface through which the trocarpasses, and the cannula is introduced with the trocar through the holecreated by the trocar. The pointed trocar is one of the principal causesof injuries to abdominal viscera during laparoscopy, as described above.

The principal object of the present invention is to provide a safe,easy-to-use, easy-to-maintain and inexpensive apparatus for, and methodof, gaining access to body cavities for endoscopic procedures whichavoids the above-described disadvantages presented by currently knowndevices.

Another object of the invention is to provide a cannula for the purposeof accessing the peritoneal cavity, wherein the distal end of thecannula comprises a means for cutting and penetrating the layers of thebody wall to gain entry into the peritoneal cavity, without the need fora trocar.

A further object of the invention is to provide a method for insertingthe cannula through the abdominal wall and into the peritoneal cavitywhereby the progress of the cannula occurs via rotational movementthrough the layers of the body wall including the peritoneum, ratherthan by a force applied at substantially 90° to the body wall. Thisrotational entry of the cannula substantially lessens the potential fordamage to the tissues and organs during endoscopy.

The present invention has advantages relating to environmental issues,more specifically to the disposal of used and contaminated cannulae andthe cost thereof. Disposal of a cannula made from environmentallyfriendly, biodegradable materials is simple and inexpensive.Furthermore, the reusable form of the cannula or a portion thereof issafe for use after sterilization, and decreases the enormous number ofused contaminated instruments which must be disposed of.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a cannula whichhas a lumen extending throughout its length and screw threads on itsouter surface. The cannula has a distal end and a proximal end, thedistal end comprising means for perforating, cutting and penetratinglayers of the body wall to gain access to a body cavity without the useof a trocar. The invention is also directed to a method for gainingaccess to a body cavity using a cannula without a trocar, comprising thesteps of (a) providing a cannula having an inner lumen extendingthroughout its entire length, the cannula having a distal end and aproximal end, the distal end comprising means for cutting andpenetrating tissue layers of the anterior abdominal wall and allowingthe distal end of the cannula to safely access the peritoneal cavity byrotational movement without the use of a trocar or obturator, thepenetrating means comprising at least one hook having a tip that may besharp or blunt, an upper margin and a lower margin, the upper marginbeing blunt in part and sharp in part, sharp for its entire length orblunt for its entire length, and the lower margin being blunt in partand sharp in part, sharp for its entire length or blunt for its entirelength, (b) making a small incision in the skin and the underlyingtissues down to the anterior fascia, sufficient in size to allow passageof the cannula, (c) making a smaller incision than in step (b) in theanterior fascia to create a window therein, the window being sufficientin size to accommodate and engage the tip of the hook of the cannulajust below the fascia, (d) placing the distal end of the cannula againstthe tissues exposed by the hole in the anterior fascia, (e) engaging thetissues of step (d) with the tip of the hook and (f) rotating theproximal end of the cannula in the direction in which the point of thehook is pointing so that the cannula stretches the window in theanterior fascia enough to accommodate the body of the cannula whilemaintaining an airtight seal around the body of the cannula, the body ofthe cannula passing through the layers of the anterior abdominal walluntil the distal end of the cannula is disposed within the peritonealcavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The object and advantages of the present invention will become morereadily apparent upon reference to the following detailed descriptionwhen considered together with the accompanying drawings, wherein:

FIG. 1 is a perspective view of a cannula with a head portion, inaccordance with the invention.

FIG. 2 is a top view of a skin incision and a smaller incision in theanterior fascia below it.

FIG. 3 is a longitudinal cross-sectional view of the anterior abdominalwall showing the distal portion of the cannula prior to its entry intothe peritoneal cavity, in accordance with the invention.

FIG. 4 is a longitudinal cross-sectional view of the anterior abdominalwall showing the distal end of the cannula disposed in the peritonealcavity, in accordance with the invention.

FIG. 5 is an elevational view of another form of a cannula and alongitudinal cross-sectional view of the head portion of the cannula inaccordance with the invention.

FIG. 6 is a perspective view of a cannula in accordance with theinvention.

FIG. 7 is a cut, partial sectional view showing the head portion of thecannula.

FIG. 8 is an exploded elevational view of an embodiment of the cannulain accordance with the invention, wherein the head portion is detachablefrom the body portion of the cannula.

FIG. 9 is an enlarged view of the distal end of the cannula shown inFIG. 3.

FIGS. 10-30 are enlarged views of the distal end of alternativeembodiments of the cannula in accordance with the invention.

FIG. 31 is a partial elevational view of a cannula in accordance withthe invention, having a tapered distal portion.

FIG. 32 is an enlarged partial view of the body of a cannula inaccordance with the invention, wherein the body of the cannula bearsscrew threads arranged in two helices.

FIGS. 33 and 34 are enlarged end views of alternative forms of thedistal end of the cannula shown in FIG. 32.

FIG. 35 is an elevational view of a cannula, with a serrated headportion, in accordance with the invention.

FIG. 36 is an enlarged partial view of the body of a tapered cannula inaccordance with the invention, wherein the body of the cannula bearsgrooves on its outer surface.

Where appropriate, like elements in the figures have been numbered withlike reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

The present invention solves the long-felt problems and fulfills theattendant needs existing in the field of the invention as discussedabove.

The present invention is directed to devices for gaining access to bodycavities, i.e. for endoscopy with or without videoscopy. The inventionwill be described with reference to FIGS. 1-36. FIG. 1 shows a cannula 1having a proximal end 2 and a distal end 3. The proximal end 2 of thecannula 1 bears a head portion 4 which is attached to a body portion 6at point 4b. The body portion 6 terminates at the distal end 3 of thecannula, the distal end 3 bearing means for penetrating and cutting thelayers of the anterior abdominal wall to gain access to the peritonealcavity. A continuous lumen 10 shown by interrupted lines 10a extendsthroughout the entire length of the cannula 1. The peripheral portion ofthe upper or free edge 4a of the head portion 4 is covered by adiaphragm 12. The central portion of the diaphragm 12 has an opening 14through which the lumen 10 of the cannula 1 communicates with theexternal environment. A gas or fluid inlet valve 16 mounted on the headportion 4 couples a hollow tube 16a to the lumen 10 of the cannula. Agas source (not shown) may be attached to the hollow tube 16a. The valvehandle 16b opens and closes the valve 16 to control the flow of gas intoand out of the cannula 1. A flap-valve (not shown) or other sealingmeans to close off the lumen is disposed within the head portion belowthe diaphragm. The outer surface of the body portion 6 of the cannula 1is provided with screw threads 18 which have rounded edges, and do notextend all the way down to the distal end 3. The screw threads may bearranged in a helix and may be disposed on the entire outer surface or aportion thereof. The screw threads may have cutting, blunted or roundededges, may be broader at their bases or their top portions, andfacilitate the stretching of the anterior fascial window and spreadingof the tissues as the cannula traverses the layers of the body wall.

The terminal portion of the distal end of the cannula bears a hook or aprotrusion, the hook or protrusion having a pointed or a rounded tip.The hook or protrusion has a lower free margin, and an upper marginwhich connects the tip of the hook with the remainder of the cannula.The tip of the hook and/or part or all of the upper margin and/or partor all of the lower margin constitute the means for perforating, cuttingand penetrating the layers of the anterior abdominal wall, allowing thedistal end of the cannula to enter the peritoneal cavity. The entireupper and/or lower margin may be blunt or sharp; alternatively, only aportion of the upper and/or lower margin may be sharp. Furthermore, thecutting surface of the sharp margin may be beveled, with the bevelfacing inwards towards the lumen of the cannula, or outwards i.e. awayfrom the lumen. In FIG. 1, the hook 8 at the distal end 3 has a roundedtip 8a and a sharp upper edge 8b. The lower edge 8c is blunt.

A preferred embodiment comprises a hook having a rounded tip, a bluntlower margin, a sharp cutting edge on the upper portion of the uppermargin and a blunt, non-cutting edge on the lower portion of the uppermargin i.e. the portion of the upper margin that abuts the rounded tip.The potential for trauma to the tissues is minimal because the roundedtip, blunt lower margin and blunt lower portion of the upper margin havethe effect of simply pushing the tissues and organs ahead of the cannulain the peritoneal cavity. The screw threads on the outer surface of thebody of the cannula extend to the distal end. The presence of a screwthread at the distal end thickens, and therefore strengthens, the lowermargin, including the tip of the hook. The threads have rounded edgeswhich further minimize damage to the tissues. The top of each screwthread is broader than its base. Thus, the screw threads act likeflanges in the peritoneal cavity and the abdominal wall, and whentraction is applied to the proximal end of the cannula or to theinstruments inserted through the cannula, the screw threads help tomaintain the position of the cannula and prevent the distal end of thecannula from slipping out of the peritoneal cavity.

In another preferred embodiment, having a hook with a rounded tip and ablunt, non-cutting upper margin, the rounded tip engages the tissuesdeep to the fascial layer, and by repeated rotation of the cannula, therounded tip penetrates the inner tissue layers and enters the peritonealcavity.

The method of use of the cannula will be described with reference toFIGS. 2-4. As shown in FIG. 2, a small incision 202 is made in the skin204 sufficient in size to accommodate the transverse diameter of thecannula not shown. The incision may include the subcutaneous tissues 206down to the anterior fascia 208; alternatively, the subcutaneous tissues206 may be separated by blunt dissection. An even smaller incision 210is then made in the anterior fascia, creating a window sufficient insize to accommodate and engage the tip of the hook of the cannula (notshown) just below the anterior fascia 208. FIG. 3 shows the distalportion of the cannula 1 which has been inserted through the skinincision 202, so that the tip 8a of the hook 8 and lower margin 8c ofthe cannula contacts the tissues 212 exposed by the hole 210 in theanterior fascia 208, and the tip 8a of the hook 8 engages the tissues212. FIG. 4 shows the position of the cannula 1 after the proximal end(not shown) of the cannula has been repeatedly rotated, maintainingsufficient pressure on the proximal end of the cannula in the directionin which the tip 8a of the hook 8 is pointing, to allow the penetratingmeans, the diameter of the cannula 1 and the screw threads 18 to cut andstretch the window or hole 210 in the anterior fascia 208 to accommodatethe body 6 of the cannula 1 while maintaining an airtight seal aroundthe body of the cannula. The user continues to rotate the proximal endof the cannula so that the cannula passes through the tissue layers 212deep to the anterior fascia 208 until the distal end 3 of the cannula 1is disposed a short distance within the peritoneal cavity 216. Therotational force applied can easily be regulated and controlled by theuser to ensure that the force used is just sufficient to allow thedistal end to perforate the peritoneum 214 and to enter the peritonealcavity 216. As described in this paragraph, the cannula is the firstinstrument to be inserted through the incisions into the peritonealcavity. Alternatively, the cannula may be inserted only after a Veressneedle has been inserted through the incision, the peritoneal cavity hasbeen insufflated with gas via the Veress needle and the Veress needlehas been withdrawn therefrom.

Furthermore, while the cannula and method of using it are described withreference to the peritoneal cavity, it should be understood that theapparatus and method of the invention are directed to endoscopic accessto any body cavity that can be accessed by such an instrument, forexample, but not limited to, the pleural cavity, the pericardial cavity,the extradural cavity, the mediastinum, joint spaces and theretroperitoneal cavity.

It is also possible to insert the laparoscope (attached to a lightsource) and video monitor into the proximal portion of the cannula, sothat as the cannula is advanced through the tissues of the abdominalwall and into the peritoneal cavity, the distal end of the cannula andthe tissues ahead of the cannula can be observed by the user through thelumen of the cannula or on the video monitor as the cannula advances. Inthis way, the cannula is introduced under vision.

There are many embodiments of the invention which will be described withreference to the figures.

FIG. 5 shows a cannula 1 having a substantially rectangular-shaped headportion 4. The longitudinal cross-sectional view of the head portionshows the presence of a continuous lumen 10 extending the length of thecannula. The screw threads 18 are wider at their base 18a than at theirupper surface 18b, and the screw threads have a sharp cutting edge 18c.The hook 8 at the distal end 3 has a pointed sharp tip 8e and a bluntupper margin 8d.

FIG. 6 shows the lever 24 that opens and closes the flap-valve (notshown) discussed above. Screw threads 18 extend all the way to thedistal end 3 of cannula 1. The hook 8 has a pointed sharp tip 8e and asharp upper edge 8b.

FIG. 7 shows a flap-valve 20 which, in the closed position, closes offthe lumen of the cannula, thereby preventing gas or fluid from escapingfrom the peritoneal cavity before the introduction of instruments intothe lumen 10 of the cannula 1 through the head portion 4 or wheninstruments are withdrawn therefrom. Further, when the flap-valve 20 isin the closed position 20a, the operating room personnel are protectedfrom spray contamination which would otherwise occur by body fluidsescaping through the proximal end of the cannula. The flap-valve 20 isshown in the closed position 20a, sealing the lumen 10 and in the openposition 20b, where the lumen communicates with the externalenvironment. When the flap-valve 20 is open, instruments can be insertedinto or withdrawn from the cannula 1 and gas can freely escape from thebody cavity.

The cannula may be manufactured as a single entity, comprising a headportion and a body portion attached to and integral with the headportion. Alternatively, the body portion may be attached to the headportion by attachable means including, but not limited to, screw-in orclip-on means such that the body portion is detachable from the headportion. The attachable means may allow a head portion to be used withbody portions of varying sizes. FIG. 8 shows a cannula 1 which has headand body portions which are detachable from one another. The headportion 4 bears threads 30 which screw into a portion 6a of the bodyportion 6, the portion 6a having internal threads (not shown) to receivethreads 30.

The cutting and penetrating means at the distal end of the cannula cantake various forms, some of which are illustrated in FIGS. 9-30.

FIG. 9 shows the features of the distal portion of the body 6 of thecannula 1 shown in FIG. 8. Screw threads 18 are wider at their uppersurface 18d than at their base 18e and the screw threads 18 extend tothe distal end 3, the most distal screw thread 18z increasing thethickness of the free lower margin 8c of hook 8. The hook 8 has arounded (blunt) non-traumatic tip 8a and the upper margin of the hook 8has a blunt area 8d which abuts the tip of the hook and a sharp area 8bdisposed on the portion of the hook which is adjacent to the junction 8jof the hook and the remainder of the body of the cannula 1. The sharparea 8b facilitates enlargement of the anterior fascial window enough toaccommodate the cannula's threaded body, while an airtight seal ismaintained between the cannula and the tissues.

FIG. 10 shows the features of the perforating, cutting and penetratingmeans 8 of a cannula 1, wherein the hook 8 has a pointed tip 8e, a sharpupper margin 8b and a blunt lower margin 8c.

FIG. 11 shows the features of the distal portion of the body portion 6of a cannula 1. The screw threads 18 do not extend to the distal end 3,and the portion of the body 6 towards the distal end 3 of the cannula 1is thus bare of threads. The screw threads 18 are broader at their base18a than at their upper surface 18b.

FIG. 12 shows the features of the distal portion of the body portion 6of a cannula 1, wherein the cannula extends distally beyond the mostdistal thread, except at the tip 8a of the hook 8 where the distalextension of the cannula beyond the most distal thread 18z tapers sothat it fuses with the tip of the hook 8 at point 102.

FIG. 13 shows the distal end 3 of a cannula 1 wherein the hook isdisposed in a more vertical direction in relation to the axis A--A, thuswidening the angle 21. The angle 21 may thus be more obtuse or acutedepending on the direction of the hook 8 in relation to the axis A--A.The most distal screw thread 18z may follow the direction of the hook,so that it fuses with the hook, increasing the thickness and thus thestrength of the lower free margin 8c of the hook 8.

FIG. 14 shows the distal end 3 of a cannula 1 which bears asickle-shaped hook 8j. The screw threads 18 extend to the distal end 3,the most distal screw thread 18z being curved so that it is convex atits base, increasing the thickness of the free lower margin 8c of thehook 8. The hook 8 has a rounded tip 8a, a sharp concave-shaped uppermargin 8 and a blunt convex lower margin 8c. The upward direction of thetip 8a further decreases the potential for injury to tissues.

FIG. 15 shows a configuration at the distal end 3 of a cannula 1 whichis similar to FIG. 12, except that this embodiment has a double cuttingedge, the hook 8 having a sharp lower margin 8p which facilitatescutting the tissues that are contacted by the distal end 3 of thecannula 1 and an upper margin 8b which is sharp along its entire length,the sharp upper margin 8b being angled so that the portion of the uppermargin 8b adjacent to the tip 8a of the hook 8 is less vertical than theremainder of the upper margin 8b in relation to the axis A--A.

FIG. 16 shows the distal portion of a cannula 1 wherein the screwthreads 18 extend to the distal end 3, the most distal screw thread 18zincreasing the thickness of the free blunt lower margin 8c and the tip8a of hook 8. The hook 8 has a sharp upper margin 8b and a rounded tip8a.

FIG. 17 shows the distal portion of a cannula 1 similar to FIG. 16,except that the sharp upper margin 8b of the hook 8 is concave.

FIG. 18 shows the distal portion of a cannula 1 similar to FIG. 16,except that the sharp upper margin 8b of the hook 8 is convex.

FIG. 19 shows the distal portion of a cannula 1 similar to FIG. 16,except that the upper margin 8b of the hook 8 is angled so that theportion of the upper margin 8b abutting on the tip 8a of the hook 8 isless vertical than the remainder of the upper margin in relation to theaxis A--A.

FIG. 20 shows the distal portion of a cannula 1 which has a doublecutting edge, the hook 8 having a sharp upper margin 8b and a sharplower margin 8p. The screw threads 18 do not extend to the distal end 3of the cannula.

FIG. 21 shows a configuration at the distal end 3 of a cannula 1 whichis similar to FIG. 20, except that the upper margin 8b and the lowermargin 8p are concave in shape.

FIG. 22 shows a configuration at the distal end 3 of a cannula 1 whichis similar to FIG. 20, except that the upper margin 8b and the lowermargin 8p are convex in shape.

FIG. 23 shows a configuration at the distal end 3 of a cannula 1 whichis similar to FIG. 20, except that the upper margin 8b and the lowermargin 8p are angled so that the portions of margins 8b and 8p abuttingon the tip 8a of the hook 8 are less vertical than the remainder of themargins 8b and 8p in relation to the axis A--A.

FIG. 24 shows a configuration at the distal end 3 of a cannula 1 whichis similar to FIG. 15, except that the most distal thread 18z and thelower margin 8c follow the same angle as the upper margin 8b.

FIG. 25 shows a configuration at the distal end 3 of a cannula 1 whichis similar to FIG. 24 except that the upper margin 8b of the hook 8, thelower margin 8c of the hook 8 and the most distal thread 8z are angledin the opposite direction to their counterparts in FIG. 24.

FIG. 26 shows a configuration at the distal end 3 of a cannula 1,wherein the upper sharp margin 8b of the hook 8 is convex, the freelower blunt margin 8c is concave, and the curve of the most distalthread 18z follows the direction of the margins.

FIG. 27 shows a configuration of the distal end 3 of a cannula 1,wherein the upper sharp margin 8b is concave, the free lower bluntmargin 8c is convex, and the curve of the most distal thread 18z followsthe direction of the margins.

FIG. 28 shows a configuration of the distal end 3 of a cannula 1, whichhas a hook 8 similar in configuration to the hook shown in FIG. 24,except that the most distal thread 18z does not extend to the distal end3 of the cannula 1 and the sharp lower margin 140 is formed by the endof the cannula 1 which is distal to the most distal thread 18z.

FIG. 29 shows a configuration of the distal end 3 of a cannula 1, whichhas a hook 8 similar in configuration to the hook 8 in FIG. 24, exceptthat the sharp lower margin 140 is formed by the end 3 of the cannulawhich is distal to the most distal thread 18z.

FIG. 30 shows a configuration of the distal end 3 of a cannula 1, whichhas a hook 8 similar in configuration to the hook 8 in FIG. 25, exceptthat the sharp lower margin 140 is formed by the end 3 of the cannulawhich is distal to the most distal thread 18z.

The cannulae of the present invention have a diameter ranging from about1 millimeter to about 25 millimeters in diameter, more usually from 5 to15 millimeters. The lengths and diameters of the cannulae are withinranges known and used for procedures in children and adults. Thediameter of the lumen of the cannula may be uniform throughout itslength. Alternatively, the cannula may be tapered, so that the distalend of the cannula is narrower than the proximal end. With thisvariation in diameter, it is understood that means are used to maintainan airtight seal at the proximal end, even where the diameter of aninstrument inserted through the cannula is less than the diameter of theproximal end of the cannula. When this tapered cannula is used, thewindow in the anterior fascia is progressively enlarged by theincreasing diameter of the cannula from its distal to its proximal end,and an airtight seal is ensured between the cannula and the tissuesthrough which the cannula passes. FIG. 31 shows the body 6 of a taperedcannula 1, wherein the diameter of the lumen 10a of the distal portionof the body is less than the diameter of the lumen 10b of the moreproximal portion of the body.

FIG. 32 shows the distal portion of a cannula 1, wherein the body 6 ofthe cannula 1 bears screw threads arranged in 2 helices. The first helix120 and the second helix 130 are in the same plane and parallel to oneanother. The screw threads 18m of the first helix 120 are disposedbetween and are parallel to the screw threads 18n of the helix 130. Thescrew threads 18m of the first helix 120 and the screw threads 18n ofthe second helix 130 extend to the distal end 3 of the body, the mostdistal screw thread 18z₁ of the first helix 120 terminating in hook 8vand the most distal screw thread 18z₂, of the second helix 130terminating in hook 8w.

FIG. 33 shows the distal end of the cannula depicted in FIG. 32 as seenend-on from the distal end 3. Hooks 8v and 8w have rounded tips 8a₁, and8a₂ respectively.

FIG. 34 shows an end-on view of the distal end of a cannula having asimilar configuration to the cannula depicted in FIG. 32, except thatthe hooks 8v and 8w have pointed tips 8e₁, and 8e₂ respectively.

FIG. 35 shows a cannula 1 of the invention, wherein the most proximalportion of the head 4, i.e. the portion of the head adjacent to andincluding the upper or free edge 4a of the head portion 4, has aserrated outer surface 5 which enables the user to grasp the head firmlywhile rotating the cannula 1. The entire head portion or any portionthereof may have a serrated surface. The presence of a serrated portionprevents the head portion from slipping from the user's grasp, as mayoccur when using a cannula which has a head portion with a smooth outersurface.

FIG. 36 shows a portion of the body 6 of a cannula 1, wherein the outersurface of the body 6 has grooves or depressions 19 instead of screwthreads as described above. If the anterior fascia should slip into agroove or depression, an airtight seal is maintained, as the anteriorfascia recoils slightly from its prior position due to its inherentslight elasticity.

The cannulae of the invention may be made from any of the materials usedin the field including, but not limited to, teflon, natural rubber,synthetic rubber, plastics and thermo-plastics including, but notlimited to, polyvinylchloride, polyethylene, polyurethane or the like,or metals including, but not limited to, aluminum or stainless steel.The materials used may be rigid or flexible. Thus, the entire cannulamay be rigid or flexible. Alternatively, the cannula may comprise arigid portion and a flexible portion, for example, but not limited to, arigid head portion and a flexible body portion or flexible head and bodyportions and rigid screw threads. The tube may be made from any inertmaterials used in this field, and the materials used may be opaque orclear. The cannula may be radiopaque or radiolucent. Alternatively, aradiolucent cannula may have a radiopaque tip. Any or all of the screwthreads, or any parts thereof, may be radiopaque.

The cannulae of the invention may be disposable or reusable. In theembodiments of the invention having a body and a head which aredetachable, an example of which is shown in FIG. 5, the head portion maybe reusable and the body portion disposable, or vice-versa.Alternatively both portions may be reusable or disposable. Furthermore,the body of the cannula may be rigid. Alternatively, the body of thecannula or a portion thereof may be flexible. Because the head portionof the cannula is expensive to manufacture, the most economicalembodiment comprises a reusable head portion which can be attached toseveral sizes of disposable body portions.

Cannulae presently in use may be modified in accordance with the presentinvention. For example, the cannula of the present invention couldreplace the Veress needle and its cannula, thus avoiding possible traumaproduced by the Veress needle. Furthermore, cannulae in accordance withthe present invention can be compatible with or adapted to otherinstruments disclosed for video laparoscopic and/or other endoscopicprocedures. For example, the cannula of the invention can have gradationmarks on its outer surface to indicate the depth of the distal end ofthe cannula from the surface of the body. Furthermore, the outer surfaceof the cannula may bear projections which prevent the cannula from beinginserted into the body cavity beyond the desired depth.

The description of the above embodiments is meant to be illustrative ofthe scope and spirit of the invention. These embodiments will makeapparent other embodiments and examples which are within contemplationof this invention.

I claim:
 1. A cannula for accessing a body cavity said cannula having adistal end and a proximal end, a lumen within the cannula extendingthroughout its entire length, the distal end comprising means forpenetrating tissue layers of a body wall to access the body cavity,wherein said lumen is sufficiently large throughout its length to allowpassage of instruments directly into the body cavity and wherein saidpenetrating means is peripherally situated.
 2. A cannula according toclaim 1 wherein the cannula includes a head portion at its proximal endand a body portion attached to and extending from the head portion tothe distal end of the cannula, the head portion comprising an inlet forgas and a valve means, the valve means preventing escape of gas andfluid from the body.
 3. The cannula according to claim 2 wherein thebody portion of the cannula tapers from a point along its length to thedistal end of the cannula, whereby the diameters of the body portion ofthe cannula and its lumen are smaller at its distal end than at saidpoint.
 4. A cannula according to claim 2, wherein the body portion ofthe cannula has at least one screw thread around its outer surface.
 5. Acannula according to claim 4 wherein the body portion of the cannula hasa first and second helix of screw threads around its outer surface, thescrew threads of the second helix being disposed between the screwthreads of the second helix, the screw thread of each helix terminatingin a hook at the distal end of the cannula.
 6. A cannula according toclaim 2, wherein the head portion and body portion are attached by meanswhereby they can be detached from and re-attached to one another.
 7. Acannula according to claim 6, wherein the head portion is attached tothe body portion by screw-on means.
 8. A cannula according to claim 6,wherein the head portion is attached to the body portion by clip-onmeans.
 9. A cannula according to claim 6, wherein the head portion isdisposable and the body portion is reusable.
 10. A cannula according toclaim 6, wherein the head portion is re-usable and the body portion isdisposable.
 11. A cannula according to claim 2 or claim 10, wherein thehead portion and body portion are re-usable.
 12. A cannula according toclaim 2 or claim 10, wherein the head portion and body portion aredisposable.
 13. A cannula according to claim 1, wherein the body cavityis the peritoneal cavity.
 14. A cannula according to claim 1, whereinthe penetrating means at the distal end comprises at least one hookhaving a sharp tip.
 15. A cannula according to claim 1, wherein thepenetrating means at the distal end comprises at least one hook having arounded tip.
 16. A cannula according to claim 1, wherein the penetratingmeans at the distal end comprises a hook having a sharp upper margin.17. A cannula according to claims 1, wherein the hook at the distal endhas a sharp tip and at least one cutting edge.
 18. A cannula accordingto claim 1, wherein the penetrating means comprises a hook having a tip,an upper margin and a lower margin in a combination selected from agroup consisting of a sharp or blunt tip, an upper margin that may beblunt in part and sharp in part, sharp for its entire length or bluntfor its entire length and a lower margin that may be blunt in part andsharp in part, sharp for its entire length or blunt for its entirelength.
 19. A cannula according to claim 1, wherein the lumen has auniform diameter throughout its length.
 20. A cannula for accessing abody cavity via a small incision through tissue layers of the abdominalwall, the incision at least through the anterior fascial layer beingsubstantially smaller than a transverse dimension of the cannula, thecannula comprisinga distal end and a proximal end; a lumen extendingthroughout the entire length of the cannula; means at the distal end ofthe cannula to permit the cannula to access the body cavity; and meanson the cannula to facilitate spreading of the tissues around theincision, wherein said lumen is sufficiently large throughout its lengthto allow passage of instruments directly into the body cavity andwherein the access means at the distal end of the cannula isperipherally situated.